The invention relates to an automatic clutch control system which automatically control the coupling of a driven shaft to a drive shaft in a clutch mounted on an automobile in accordance with a decision rendered by an electronic unit.
In a conventional automatic clutch arrangement, there has been proposed to achieve an accurate engagement of a clutch without experiencing a shock in a clutch arrangement in which a clutch transmits rotating power to an output shaft. The arrangement comprises a power sensor for detecting the number of revolutions of the output shaft, a clutch sensor for detecting the number of revolutions of the clutch, a comparator for determining the relative magnitude of the number of revolutions of the both sensors, a parameter of follow-up control responsive to an output from the comparator to activate the clutch for engagement as the number of revolutions of the output shaft increases whenever the number of revolutions of the output shaft is higher than that of the clutch, and an automatic engaging circuit responsive to an output from the comparator and operating whenever the number of revolutions and operating whenever the number of revolutions of the clutch is higher to deactuate the follow-up control and to terminate automatically the engagement of the clutch within a given time interval. In this manner, the relative magnitude of the number of revolutions of the engine and the clutch is determined in an electrical manner, and whenever the number of revolutions of the engine is higher than that of the clutch, an engagement of the clutch occurs in response to the number of revolutions of the engine while whenever the number of revolutions of the engine is lower than that of the clutch, an engagement of the clutch takes place in accordance with a difference therebetween. (See Japanese Patent Publication No. 26,020/1978, filed Mar. 26, 1971 and published July 31, 1978). In other words, the rotational speed of the engine is chosen as a main variable while a differential speed between the output shaft of the clutch (driven shaft) and the output shaft of the engine (the clutch drive shaft) is chosen as a parameter for controlling the clutch coupling power. To summarize, in a mode in which the vehicle is driven for running under the engine power, the clutch coupling power is controlled in a manner corresponding to the rotational speed of the engine while in an engine brake mode, the clutch coupling power is controlled as a particular function of time. Consequently, the slip rate of the clutch depends on the rotational speed of the engine, and the correlation between the engine power and a load on the vehicle may not be proper.
To achieve a proper engagement of a clutch for various running conditions of a vehicle, U.S. Pat. Nos. 4,518,068, 4,529,072 and 4,475,637 filed Mar. 12, 1982 disclose a system for controlling the pressure with which a clutch is engaged, with a slip rate e of the clutch, which is equal to the ratio of the rotational speed No of a driven shaft against the rotational speed Ne of a drive shaft, as a main parameter. The slip rate e corresponds to the rotational speed No and Ne of the driven shaft and the drive shaft respectively, therefore the clutch coupling power corresponds to running condition of the vehicle. A microprocessor of the sysetem, in the first clutch control, initially applies to the clutch an engaging force of a reduced magnitude to detect the rate of change (dNe/dt) of the rotational speed Ne of the clutch drive shaft, which is utilized as indicative of the correlation between the loading and the engine power in determining a clutch turn-on response. Throttle opening is used to determine the engine power. The combination of the vehicle load and the engine power specifies a particular data group (Vsx=f(t)) having a proper clutch ON change rate (dVs/dt) in the first time segment l=0. The clutch controlling signal Vsx is changed at a time subinterval of .DELTA.T=0.05 sec. In the segment l=0, ##EQU1## After proceeeding through the segment l=0, the clutch ON control enters the second time segment l=1. During the clutch ON control for the second time segment l=1, the actual slip rate e is utilized as indicative of the vehicle load, and the throttle opening is utilized as indicative of the engine power in the same manner as in the first time segment. These specify a particular group of clutch controlling data Vsx=f (t) having a proper clutch ON change rate (dVs/dt) for the second segment l=1. The clutch control signal V.sub.sx is changed at a time subinterval of .DELTA.t=tt sec. In the second segment l=1, ##EQU2## or 0.8 sec. After proceeding through the time segment l=1, the clutch ON control in the third time segment l=2 is entered. This takes place in the similar manner as during the time segment l=1. A similar clutch ON control is repeated for the segments l=3, 4, . . . .
The aforesaid clutch control is executed by a microcomputer system having a center processing unit CPU (microprocessor or microcomputer), RAM and ROM. A program for executing the clutch control is stored in a ROM of CPU and/or an additional ROM. Also the data groups each of which will be specified by the throttle opening and the vehicle load dNe/dt as well as the data group each of which will be specified by the throttle opening and the actual slip rate e=No/Ne are stored in the additional ROM. Each of the data groups includes 8 data which will be read out in order and have a specific change rate. Selection of a data group in turn and reading out of each data therein causes an increment of the clutch coupling power with a change rate which corresponds to the throttle opening as well as the vehicle load or the actual slip rate.
The system initially applies to the clutch a slight engaging force to detect the vehicle load as described hereinbefore, however, the vehicle may experience uncomfortable shock because the vehicle does not start running and the rotational speed Ne of the engine rises up when the throttle opening is small and the vehicle load is heavy, then the vehicle starts and the rotational speed Ne of the engine falls rapidly when the throttle opening becomes large, thus the rotational speed Ne of the engine rises and falls in turn.